Temperature indicator



Nov. 12, 1935. G. H. Ems ET AL 2,020,676

TEMPERATURE INDICATOR 7 Filed Feb. 8, 1953 Patented Nov. 12, 1935 TEMPERATURE mmca'ron I George Holland Ellis and Alexander James Weason, Spondon, near Derby, England, assignora to Celanese Corporation of America, a corporatlon of Delaware Application February a, 1933, Serial in. 655,851

' In Great Britain February 25, 1932 i 9 Claims. (0;. 73-32) This invention relates to the control of temperature in textile and other operations and more particularly to indicators for use in the control of temperature in such operations. In many operations involving a raised temperature, and in particular finishing operations performed on fabrics, it is important to maintain a fairly strict control over the temperature employed. This is particularly the case in such op-- erations as ironing and calendering and especially where the materials under treatment are made of or contain yarns of a thermoplastic character,

- for example, yarns of cellulose acetate or other cellulose ester or, ether, e. g. cellulose formate,

propionate or butyrate or ethyl or benzyl cellulose, when slightly too high a temperature leads to complete destruction of the material.

The object of the present invention is to. ro

vide an indicator which may be employed to give a visual indication of temperature, e. g. the temperature-of a device, for example an iron or calenrler employed in textile and other operations, and the invention consists in an indicator giving indications of the temperature of a surface comprising a mass of a composition containing a fusible and/or sublimable substance or mixture of substances and a filler.

In textile operations the temperature to be indicated will usually be the maximum temperature at which it is desired to conduct the operation. Preferably the fusible substance should fuse and the sublimable substance sublime freely in the neighbourhood of the temperature it is required to indicate.

on application of the indicator to a surface the mmperature of which is above the melting point of the fusible substance or substances, or of their subnc point if they sublime, a visible marl: is made on the emface owing to the transference of filler to the surface.

By a suitable choice of the fusible material, which may be a single substance or a mixture of substances and of the relative proportions of that material and of the iiller, a wide range of indications may be obtained. For example, the

} indicator may be of such composition that if no marl: is left on the surface showing that no melting and no transference of filler has taken place, the temperatureis too low, whilst when there is a dense maria the temperature will be too A, light or less definite mark may be taken to'indicate that the correct temperature is being employed.

Preferably the materials to be employed should be such that they can be readily removed from Elli -215 C), metallic selenium l Ell 0.)

the surface, and substances which sublime at about the working temperature of the heated surface are particularly valuable since they automatically disappear from the surface. Fillers such for example, as chalk, fuller's zinc oxide and powdered pigments are easilyre movable fromthe surface by simple wiping, especially when used in. conjunctioni with substances that sublime. Where coloured markings are desired, it is preferred to employ in admix l0 ture with the filler, such for example as chalk, fullers earth or zinc oxide, dyestuffs which are converted to the fluid form and/or which change color at about the temperature of. the heated surface at which it is desired towcrk. Such dyelli stufls, if convertible to the fluid form, maybe employed as sole fusible and/or sublimable components ofthe composition or in conjunction with other suchcomponents. Examplesof dyestuffs which have been found suitable for use in lac-.20,

cordance with the present invention are Lithol Fast Yellow 26-, Sudan 26, Fast, Oil Grange T, Fast Oil Scarlet 2R, Parachlorortlionitroaniline and 2:6 dinitro-i-methylaniline. By a suitable choice of a volatile dyestuff it is possible to pre- :5 pare an indicator which will leave a coloured mark, the colour of which is comparatively last,- ing, at about the working temperature, and which will leave a mark the colour of which will disappear in a few seconds it the temperature be too 30 high.

Substances having a suitable melting point for use as indicators in the .l: shins oi cellulose acetate materials whose thermoplastic nature necessitates considerable care in finishing operations, :5 include for example, bismuth tribromide (M. P

potassium pyrosulphite (M. P. 21W 83.), paraazophenol (M. P. 217 C9, l:il cilantro-naphthalene (M. P. 210 fl), anthraquinone disulphomc so acid (M. P. 21o 6.), and anthem-cue (M. P. 216 6,), 6f these, anthracene is particularly suitable, since it has the desirable prcmrty mentioned above of subliming after melting; as well as being comparatively cheap. It desired the w melting point oi the fusible substance may be lowered by the addition of other substaneea, Thus for example, naphthalene may be aed with the embrace-no to give a reduction oithe melting point. The proportion oi naphthalene ea or other substance should not be such, however, as to the att activeness or? the anthracene. A suitable composition containing anthrenene and naphthalene has been found to consist of 10 parts of anthracene, l d pail-s, e. fl parts of naplv 5 earth and .J

thalene and -14 parts of chalk. A composition containing equal parts of anthracene and zinc placeleaving a light deposit of chalk. At 220 C. a thick dense chalk mark is made on the surface, the anthracene subliming from the surface and leaving the chalk in a. condition in which it is easily removed by slight rubbing with a cotton pad. The above mentioned composition containing 4 parts of naphthalene in addition to 10 parts of anthracene gives corresponding marks at a temperature about five degrees lower than those for the straight mixture of anthracene and chalk.

The composition may be made up in any suitable form, a very convenient form being that of a pencil, and may, if desired, be contained in any convenient type of holder, e. g. a metal, paper or wooden holder. The blocks, pencils, or other forms adopted for the indicator may be prepared by any convenient method. Thus, for example, equal parts of anthracene and precipitated chalk may be mixed, whilst the anthracene is in a molten condition, and the fused mass cast into moulds. Since it is desirable that the composition should be uniform throughout, the heavier brands of chalk should be avoided in such a process. It has been found. very effective however, to grind the fusible material and filler,

and mould them to the desired form under heat and/ or pressure. It isfound here also that particle size plays a large part in the production of a stick possessing the necessary strength to withstand handling. Thus large particles produce sticks of a brittle nature. A very good method of preparing the constituents has been found to be "to grind them in aball mill before moulding.

The introduction of waxes, e. g. one per cent of carnauba wax, into the mixture facilitates the removal of the sticks from the mould. The

'moulding may be carried out by any convenient tion of sticks suitable for use as temperature indicators in accordance with the present invention, but is in no way limitative:--

Example A composition containing anthracene pounds, chalk 15 pounds, and carnauba wax 4% 02s., is ground with iron balls in asteel mill for two hours, and then passed through a .40 mesh gauge. Two pounds of the mixture is then placed in an open steam heated steel mould designed to make fifteen rods, 16 inches long, and pressed under a pressure of ton per square inch, 90 pounds of steam pressure being maintained. After twenty minutes the steam is turned off and the mould cooled for two minutes with cold water. The sticks are then removed while still hot. The

J .16" sticks may then be cut up into convenient be made which, by suitable choice of the fusible and/or sublimable constituents, may be utilized correct or whether it is too high.

for indicating other temperatures or ranges of temperature.

The use of the indicators of the present invention may be illustrated by the accompanying drawing. Theindicator-in pencil form I wrapped I for part of its length in a stiff paper holder 2 is drawn sharply down the heated iron I when the heaviness of the mark 4 left by the indicator indicates whether the temperature of the iron is 10 What we claim and desire to secure by Letters Patent is:-

1. A device for giving information regarding the temperature of a surface, when brought into contact therewith, which comprises a solid mass ll containing a relatively infusible filling material and a substance which is converted into a fluid form at a predetermined temperature, thus permitting transfer of the filling material from the mass to a surface having at least that tempera- 20 ture, to term at the point of contact a visible trace capable of ready removal from the surface.

2. A device for giving information regarding the temperature of a surface, when brought into contact therewith, which comprises a solid mass 5 containing a relatively infusible filling material and a substance which volatilizes at a predetermined temperature, thus permitting transfer of the filling material from the mass to a surface having at least that temperature, to form at the point of contact a visible trace capable of ready removal from the surface.

3. A device for giving information regarding the temperature of a surface, when brought into contact therewith, which comprises a solid mass containing a relatively infusible filling material and anthracene, which latter, by reason of its conversion into a fluid form at a definite temperature, permits transfer of thefiliing material from the mass to a surface having at least that temperature, to form at the point of contact a visible trace capable of ready removal from the surface.

4. A device for giving information regarding the temperature of a surface, when brought into contact therewith, which comprises a solid mass 46 containing a relatively infusible filling material and a mixture of anthracene and naphthalene, which mixture, by reason of its conversion into a fluid form at a definite temperature, permits transfer of the milling material from themass to 50 a surface having at least that temperature, to form at the point of contact a visible trace capable of ready removal'from the surface.

5. A device for giving information regarding the temperature of a surface, when brought into contact therewith, which comprises a solid mass containing a relatively infusible filling material,

a coloring matter and a substance which is converted into a fluid form at a. predetermined temperature, which substance permits transfer of 06 the filling material and the coloring matter from the mass to a surface having at least that temperature, to form at the point of contact a. visible trace capable of ready removal from the surface.

6. A device for giving information regarding to the temperature of a surface, when brought into contact therewith, which comprises a solid mass containing a relatively infuslble filling material, anthracene, and a coloring matter whose color changes at a temperature in excess of the melting point of 'anthracene, the anthracene, by reason of its conversion into a fluid form at a definite temperature, permitting transfer of the filling material and the coloring matter from the mass to a surface having at least that temperatm-e. to

form at the point ofcontact a visible trace differing in appearance according tot-he temperature of the surface and capable of ready removal from the surface.

7. A device for giving information regarding the temperature of a surface, when brought into contact therewith, which comprises'a solid mass containing a relatively infusible filling material, anthracene, and a coloring matter which volatilizes at a temperature in excess of the melting containing substantially equal proportions of chalk and anthracene, which latter, by reason of its conversion into a fluid form at a definite temperature, permits transfer of the chalk from the mass to a surface having at least-that tem- L perature, to form at the point of contact a visible trace capable of ready removal from the surface.

9. A. device for giving information regarding the temperature of a surface, when brought into contact therewith, which comprises a solid mass w 7 containing equal proportions of chalk and a mixture of anthracene and naphthalene containing less than 30% of naphthalene which mixture, by

reason of its conversion into afiuid form at a definite temperature, permits transfer of the chalk 15 from the mass to a surface having at least that temperature, to form at the point of contact a visible trace capable of ready removal from the surface.

GEORGE HOLLAND ELLIS.

20 ALEXANDER JAMES WESSON. 

